Compressor



Nov. 23, 1954 w. w. PAGET 2,695,132

COMPRESSOR Filed June 25, 1948 4 Sheets-Sheet 1 Big. 1. 202

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4 Claims. (Cl; 230-183) This invention relates to gas pumps, especially to air compressors of the two-stage type.

There are many industrial uses for compressed air, and efiicient, reliable compressors are in considerable demand. One of the problems associated with the supply ofcompressed air concerns the fact that the temperature of theair increases materially in the compression process, and the increased temperature of the air results in increased volume; or, to put it another way, the increase in temperature itself causes a pressure increase which is lost after the air has cooled down. One of the principal problems, therefore, is concerned with temperature increase during compression.

Size of the apparatus is another concern of the cornpressordesigner. It is desirable to .keep compressor size to a minimum consistent with efficient operation, in order to keep bulk and weightdown. Accordingly, another problem is the arrangement of the compressorelements in the manner which'will providemost efl'lcient operation for a given size and weight.

In a compressor made according to this invention, the high pressure and low pressure stage cylinders are closely adjacent, and are so arranged that the two pistons in 'fact reciprocate in communicating spaces. Inasmuch as the two pistons displace different volumes, there is a volume differential, on each strokewhich gives a pumping action. Unless the. pumping action is taken into account, it can result in substantial power losses.

It is accordingly among the objects of the invention to provide a two-stage air compressor having such a new and improved arrangement of elements as to permit a minimum of temperature increase during the compression of the air and to provide for a maximum of efiicient operation with a minimum of weight, and with occupation. of a minimum of space. It is another object of this invention to provide a two-stage .air compressor in which losses arising out of the unproductive pumping of air are substantially eliminated. These and other objects are accomplished in a two-stage air compressor in which coaxial highand low pressure stages are operated from a single crank through a common piston rod; in which cooling between stages is provided for by an efi'icient arrangement of parts including an intercooler; and in which the repeated unproductive movement of entrapped air is largely obviated by a valve mechanism and arrangement which permits the escape of entrapped air and prevents the admission of air directly from the atmosphere.

In the drawings:

Fig. l is a longitudinal section view through a compressor embodying the invention;

2 is a view in section on the planes of line 22 of 1g.

Fig. 3 is a view in section substantially on the plane of lines 3-3 of Fig. l, with one of the valve discs and its spring removed;

Fig. 4 is a view in section on the plane of line 4-4 of Fig'. 2;

Fig. 5 is a view in section substantially on the planes of line 55 of Fig. 3;

Fig. 6 is a view in section substantially on the planes of line 6-6 of Fig. 3;

Fig. 7 is a view in section substantially on the planes of line 6-6 of Fig. 3, but on a smaller scale than Fig. 6 and taken lower down;

8 is a view in section on the plane of line 83 of 1g.

Fig. 9 is a view in section on the plane of line 99 of Fig. 7;

Fig. 10 is a plan view of a valve spring; and

Fig. 11 is a view'in section on the plane of line 111]l of Fig. 10.

Referring now in detail to the drawings, a crankshaft 2 is shown mounted for rotation in bearings 4 by any suitable power source connected for that purpose through a shaft 6. A connecting rod 8 changes the rotary mo.- tion of the crank throw into reciprocating motion of a crosshead indicated generally at 10. The crosshead will not be described in detail herein, but may be any of a number of suitable crossheads, such as the one shown in Patent No. 2,312,335 to Halleck, issued March 2, 1943. A piston rod 12 transmits the translatory motion of crosshead 10 to a high pressure piston 13 and a low pressure piston 14, the connection between the high and low pressure pistons being made through an extension 15 of the rod 12. The high pressure piston 13 is secured to the rod between a collar 16 and a nut 17. The low pressure piston 14 is secured on extension 15 between a collar 18 and a nut 19. The high pressure piston reciprocates in a high pressure cylinder 26, and low pressure piston 14 reciprocates in a low pressure cylinder 22. The two pistons and their respective cylinders cooperate to define a chamber which, with the structure shown, has a constantly varying volume as the pistons reciprocate.

Bearings 4 are mounted in a main frame or base 24 which has integral therewith a pedestal 26. A crosshead guide 23 is removably mounted in the pedestal 26. A cylinder block 30 is mounted on crosshead guide 28 and pedestal 26, and is secured thereto by threaded members 32. Cylinder block 30 has integral therewith an outer cylinder wall 34, and carries a removable liner 36.

A valve-containing element 4% is mounted on cylinder block 30 by means of bolts 42, and in turn low pressure cylinder block 44 is secured to valve-containing element 4%} by bolts 46. Low pressure cylinder block 44 is made up of the outer wall member 4% and a removable liner in which there is provided the aforesaid cylinder 22 to receive the reciprocating low pressure piston 14.

A stufling box 53 is shown as providing a fluid seal about the piston. rod 12. The stufling box 53 includes a number of packing rings 54 held in place in stufling box sleeve 55 by a packing gland 56. Gland 56 is secured to cylinder block 34) by studs 57 and nuts 58. Gland 56 is provided with an oil collector recess 59 and a threaded opening 60 to which a drainage conduit (not shown) may be fitted. Recess 59 is provided to collect such oil as may get past the scraper rings 61 mounted in plate 62.

Integral with cylinder block 30 there is a high pressure cylinder head 64 in which an air inlet valve 66 is removably mounted by means of a cap 68 and bolts/7i); and in which an air discharge valve 72 is removably mounted by means of a cap 74 and bolts 76. The details of valves 66 and 72 will not be described here. For an understanding of these valves, reference maybe had to Patent No. 2,2l3,259-Paget, issued September 3,

A cylinder head 78 is secured by bolts 80 to cylinder block 44 of the low pressure cylinder. Cylinder head 78 carries a pair of inlet valves, one of which is shown at 82, and is removably held in place by a cap 84 and bolts 86; cylinder head 78 also carries a pair of air discharge valves, one of which is shown at 38 and is held in place by a cap 90 and bolts 92. For a detailed understanding of valves 82 and 88 reference may be had to the above identified patent to Paget.

An intercooler indicated generally at 94 is mounted on cylinder blocks 44 and 36, there being a ribbed spacer 96 between thecasing 98 of the intercooler and the flange 106 on cylinder block Sit to which the intercooler is secured. A cover 192 is secured to casing 98 by bolts, one of which is shown at 104.

Intercooler 94 may be any of a number of satisfactory heat exchangers, and is here shown as comprising headers 106 held in place by bolts 108. Tubes 116 extend between the headers, and are here shown as covered by a plate 112, broken away in the drawing to disclose the tubes. A cooling water inlet passage 114 communicates with one header through a passage 116; the other header communicates with a cooling water outlet 118 via duct or passage 120.

Tubes 110 are preferably provided with fins for better contact with the air to be cooled. If no fins are used, bafiles 122 and 124 should be used to constrain the air flow in the direction of the arrows. If fins are used, the fins themselves may suflice to direct the air across the tubes, serving as baflles. The direction of air flow is reversed once in each of chambers 126 and 128 in cover 102, and again in chamber 130 in casing 98.

An air intake conduit 132 is secured to the first stage, or low pressure, intake 134 by bolts 136 in cooperating flanges. Intake 134 communicates with inlet valves 82 via passages 138 in the cylinder block 44 (Fig. 2) and passages in the cylinder head 78, one of such passages being shown at 140 (Fig. 4).

Discharge valves 88 empty into passages in the cylinder head 78, one of which is shown at 142, whence air flows through passages 144 in block 44 to the first stage, or low pressure, outlet 146, and thence to the intercooler. The high pressure, or second stage, inlet 148 connects the intercooler with the inlet valve 66, and high pressure conduit 150, secured by bolts 152 in cooperating flanges, is connected to the compressor discharge 154.

As will be seen from a consideration of Figs. 1 and 4, the cylindrical opening of cylinder (high pressure) is in constant communication with the cylindrical opening of cylinder 22 (low pressure); upward movement of the piston rod simultaneously moves pistons 13 and 14 and creates a partial vacuum in the space between the pistons because piston 14 displaces a larger volume than piston 13 per unit of linear travel. Similarly, downward movement of the pistons increases the pressure in the space between the pistons; if that space were at atmospheric pressure at the start of the downward stroke, the pressure would be substantially above atmospheric at the end of the stroke.

Thus, fluid between the pistons is subjected to a constant pumping action which represents useless work and which appears as heat. The heat thus generated must be removed. Accordingly, not only is power lost, but the loss of power adds to the problems of the compressor in that it adds to the total heat which must be removed by the cooling system.

This invention includes means for limiting the nonproductive pumping action to a minimum and for thus substantially eliminating the power losses arising out of such pumping. According to this means, the quantity of fluid in the space between the pistons is kept very small. provision being made to pump out of the space the fluid that leaks or blows by the piston rings.

As is best seen in Figs. 3 and 5, the valve containing element 40, referred to above, is provided with arcuate recesses or slots 156. In each slot there is an axial passage 158 (its lower end plugged as shown at 160) which is in communication with a passage 162; each passage 162 in turn opens at one end into the space between the pistons.

A bore 164 at the upper end of the passage 158 provides a seat 166 for a valve disc 168. Each disc 168 may be. and preferably is, biased against its seat by a spring 170, shown in detail in Figs. 10 and 11. Spring 170 may comprise a circular disc which is centrally punched out as at 172, and which is given a cylindrical curvature as is best seen in Fig. 11.

Arcuate recesses or slots 156 in valve containing element 40 register with the lower ends of the aforesaid air passages 138 in cylinder block 44, as is best seen in the left half of Fig. 4, thus connecting the space between the pistons with the low pressure cylinder intake via passages 162 and 158. and bore 164.

A compressor made according to this invention is preferably water-cooled. Water for this purpose is introduced into cylinder block by any suitable conduit (not shown) engaging threaded opening 174 (Fig. 7). A corresponding opening at the opposite side is plugged as shown at 176.

Cooling water flows through and fills chamber 178, passing upward through passages 180 into chamber 182, whence it flows to the low pressure cylinder block 44. Flow to block 44 is by way of valve containing element 40.

As is best seen in Figs. 3 and 6, water flows upward from chamber 182 through passages 184 in the upper end of high pressure cylinder block 30, into element 40. Element 40 has curved passages 186 which communicate with passages 184 in block 30 and with deep recesses 188 in element 40. Recesses 188 open into larger but shallow recesses 190 in the face of element 40.

Recesses 190 are in communication with passages 192 in cylinder block 44, and passages 192 open upward into chamber 194. Chamber 194 is the space between the inner wall portions 196 of outer wall member 48 and cylinder liner 50; Figs. 2 and 4.

As is best seen in Fig. 1, chamber 194 communicates with cooling water chambers 198 in cylinder head 78 through passages 200 in the upper wall of block 44. Cooling water chambers 202 are connected to be supplied with cooling water by other passages, not shown, and are centrally connected by annular chamber 204, as will be readily understood by those skilled in the art.

Arcuate recesses 206 and 208 in element 40 serve to reduce weight somewhat, and cooperate with similar recesses 210 (Fig. 5) in cylinder block 44. Arcuate recesses 212 in element 40 are located opposite the recesses 156, but recesses 212 serve no such purpose as that served by the recesses 156. Instead, recesses 212 register with the lower openings of passages 144, closing those passages at the lower end of block 44. See Fig. 4.

Cleanout holes 214 (Fig. 2) are provided in cylinder block 44. They may normally be kept covered by any suitable means as by cover plates 216.

A safety valve 218 of any suitable design is preferably provided in the circuit, as for example at the low pressure discharge as shown in Fig. 1. Valve 218 is provided with a lever 220 for the manual release of the valve.

A lubricator 222 of any satisfactory type may be mounted to be driven by the compressor crankshaft, and may be connected to supply oil by suitable conduits, not shown, to those parts requiring lubrication.

As will be understood by those skilled in the art, pistons 13 and 14 fit closely in their respective cylinders and are preferably provided with rings 224 and 226 respectively, in order to provide a substantially gas-tight seal.

Operation Air is drawn from the atmosphere by way of conduit 132, and passes into the low pressure cylinder by way of passages 134, 138, 140, and valves 82. Compressed air from the first stage leaves the cylinder by way of discharge valves 88, passages 142, 144 and 146 to enter the intercooler. The air flows across the upper ends of tubes in a direction indicated by the arrow into the chamber 126, where its direction is reversed and it flows back across the tubes as indicated into the chamber 130, where the direction of flow is again reversed and the air flows outward across the tubes again as indicated into the chamber 128; the flow is again reversed and the air passes across the lower ends of the tubes to the passage through the spacer 96.

The air which is thus cooled enters the high pressure stage by way of passage 148 and inlet valve 66. In the high pressure cylinder the air is given its final compression, and is discharged by way of discharge valve 72 and passage 154 into the high pressure conduit 150.

As was set forth above, the communicating space in the high and low pressure cylinders between the two pistons is subjected to the joint action of the high and low pressure pistons. As will be understood by those skilled in the art, the action of these pistons on the fluid in the space between them is that of compression on the downward stroke and expansion on the upward stroke. To keep the resultant heating losses to a minimum, provision is made for keeping to a minimum the quantity of fluid trapped between the two pistons. Inasmuch as a perfect seal by piston rings 224 and 226 is practically impossible, some air (or other fluid which may be compressed) is practically certain to leak past the rings. Before the quantity of air in the space between the pistons can reach any substantial proportions, it is discharged through the passages 162 and 158, and bores 164, past the valve 168 into the compressor inlet passage 138 by way of arcuate passages 156.

If the cylinder Walls become so worn as to be no longer usable, the liners may be easily replaced by new ones at a minimum of expense and trouble, and with little lost time. To this end, the low pressure stage liner is removably clamped between cylinder head 78 and valve containing element 40, and the high pressure stage liner is removably clamped between the high pressure stage cylinder head and the aforesaid element.

The advantages of a compressor made according to this invention lie in the compactness of the machine; in the ability of the machine to handle air at a desired pressure with a minimum of heat losses; and in low maintenance costs, with a minimum of time loss.

While there is in this application specifically described one form which the invention may assume in practice, it will be understood that this form of the same is shown for purposes of illustration, and that the invention may be modified and embodied in various other forms without departing from its spirit or the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent is:

1. In a compressor having an intake and a discharge, a large diameter cylinder block comprising an outer Wall member and a cylinder liner circumferentially bounding a large diameter cylinder and removably held in the outer wall member, a cylinder head engaging one end of said liner and secured to the outer wall member, an element secured to that end of the outer wall member which is opposite the cylinder head and engaging the end of the cylinder liner opposite the cylinder head, a small diameter cylinder block comprising an outer wall member and a cylinder liner removably received therein and circumferentially bounding a small diameter cylinder, means to secure the second outer wall member to the element, the second cylinder liner being engaged at one end by the element, the element having an opening therethrough whereby the large diameter cylinder communicates with the small diameter cylinder, a piston in each cylinder reciprocable in the respective liner thereof, means connecting the two pistons for simultaneous reciprocation, the pistons and liners defining, with the element, a chamher and the element having a passage therethrough which opens at one end into the chamber and at its other end to the intake, and a one-way valve in the passage through the element, said valve being spring-biased shut and openable only for fluid flow toward the intake.

2. In a multi-stage compressor comprising a plurality of single-acting piston-and-cylinder compression stages each stage having intake and discharge passages, a large diameter cylinder forming a first stage compression chamher, a small diameter cylinder forming a second stage compression chamber, the small cylinder having one end adjacent an end of the large cylinder, a closely fitting piston in each cylinder, the pistons being connected for simultaneous reciprocation in their respective cylinders, the two cylinders connected with each other at their adjacent ends to form with the pistons an intermediate chamber, the intermediate chamber having a constantly varying volume and receiving only fluid that leaks past the pistons, an element having passage means connecting the intermediate chamber exclusively with the first stage intake passage, and a valve in the passage means operable to a fully closed position to prevent fluid flow in the passage means to the intermediate chamber and 6 operable to a fully open position to freely connect the intermediate chamber with the first stage intake passage.

3. In a multi-stage compressor comprising,a plurality of single-acting piston-and-cylinder compression stages, a large diameter cylinder forming a low pressure compression chamber, a small diameter cylinder forming a high pressure compression chamber, the small cylinder having one end adjacent an end of the large cylinder, a closely fitting piston in each cylinder, the pistons being connected for simultaneous reciprocation in their respective cylinders, the two cylinders connected with each other at their adjacent ends to form with the pistons an intermediate chamber, the intermediate chamber having a constantly varying volume and receiving only fluid that leaks past the pistons, passage-providing means connecting the intermediate chamber exclusively with the atmosphere, and a valve in the passage of the passage-providing means and operable to a fully closed position to prevent fluid flow to the intermediate chamber and operable to a fully open position to freely connect the intermediate chamber with the atmosphere.

4. In a multi-stage compressor comprising a plurality of single-acting piston-and-cylinder compression stages, a large diameter cylinder forming a low pressure compression chamber, a small diameter cylinder forming a higher pressure compression chamber, the small cylinder having one end adjacent an end of the large cylinder, a closely fitting piston in each cylinder, the pistons being connected for simultaneous reciprocation in their respective cylinders, the two cylinders connected with each other at their adjacent ends to form with the pistons an intermediate chamber, the intermediate chamber having a constantly varying volume and receiving only fluid that leaks past the pistons, and means for maintaining pressure in the intermediate chamber at a minimum including passage providing means leading from the intermediate chamber and having a check valve in said passage operable to a fully open position to freely connect the intermediate chamber with the exterior of the cylinder and operable to a fully closed position to prevent fluid flow in the passage into the intermediate chamber, the intermediate chamber having its sole communication with the exterior of the cylinders through said check valve-controlled passage of the passage providing means.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 703,648 Garrison July 1, 1902 1,066,261 Diesel July 1, 1913 1,467,489 Nordberg Sept. 11, 1923 1,513,422 Raymond Oct. 28, 1924 1,520,853 Cable Dec. 30, 1924 1,580,973 Rembold Apr. 13, 1926 1,840,265 Spohrer Jan. 5, 1932 2,403,814 Maniscalco July 9, 1946 FOREIGN PATENTS Number Country Date 520,703 Great Britain May 1, 1940 837,768 France Feb. 20, 1939 

